U.S. patent number 10,801,108 [Application Number 15/687,625] was granted by the patent office on 2020-10-13 for method for fabricating ceramic matrix composite components.
This patent grant is currently assigned to Raytheon Technologies Corporation. The grantee listed for this patent is United Technologies Corporation. Invention is credited to Zissis A. Dardas, Lesia V. Protsailo, Rajiv Ranjan, Ying She, Gajawalli V. Srinivasan.
United States Patent |
10,801,108 |
She , et al. |
October 13, 2020 |
Method for fabricating ceramic matrix composite components
Abstract
A method for fabricating a component according to an example of
the present disclosure includes the steps of depositing a
stoichiometric precursor layer onto a preform, and densifying the
preform by depositing a matrix material onto the stoichiometric
precursor layer. An alternate method and a component are also
disclosed.
Inventors: |
She; Ying (Hartford, CT),
Ranjan; Rajiv (South Windsor, CT), Dardas; Zissis A.
(Worcester, MA), Srinivasan; Gajawalli V. (South Windsor,
CT), Protsailo; Lesia V. (Bolton, CT) |
Applicant: |
Name |
City |
State |
Country |
Type |
United Technologies Corporation |
Farmington |
CT |
US |
|
|
Assignee: |
Raytheon Technologies
Corporation (Farmington, CT)
|
Family
ID: |
1000005117858 |
Appl.
No.: |
15/687,625 |
Filed: |
August 28, 2017 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20190062913 A1 |
Feb 28, 2019 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B
35/565 (20130101); C23C 16/045 (20130101); C04B
35/515 (20130101); H01L 21/02529 (20130101); C04B
35/62868 (20130101); C23C 16/45544 (20130101); C04B
2235/614 (20130101); C01B 32/956 (20170801) |
Current International
Class: |
C23C
16/32 (20060101); C04B 35/80 (20060101); C04B
35/565 (20060101); C04B 35/628 (20060101); H01L
21/02 (20060101); C23C 16/04 (20060101); C23C
16/455 (20060101); C01B 32/956 (20170101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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102534491 |
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Jul 2012 |
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CN |
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0515186 |
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Nov 1992 |
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EP |
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2933353 |
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Oct 2015 |
|
EP |
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WO-2007147946 |
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Dec 2007 |
|
WO |
|
Other References
Wan, Yimao, et al., "Characterisation and optimisation of PECVD
SiNx as an antireflection coating and passivation layer for silicon
solar cells". AIP Advances 3, Mar. 21, 2013(2013), pp. 1-14. cited
by examiner .
Mainzer, Bernd, et al., "Development of wound SiCBNx/SiNx/SiC with
near stoichiometric SiC matrix via LSI process". Journal of the
European Ceramic Society 36 (2016) 1571-1580. cited by examiner
.
Patentability Search Report, conducted by MDP Research Inc. dated
Jul. 3, 2017. cited by applicant .
European Search Report for European Application No. 18191322.9
dated Dec. 17, 2018. cited by applicant.
|
Primary Examiner: Chen; Bret P
Attorney, Agent or Firm: Carlson, Gaskey & Olds,
P.C.
Claims
What is claimed is:
1. A method of fabricating a component, the method comprising:
arranging one or more preforms in a reactor; providing a
silicon-containing precursor to the reactor such that the
silicon-containing precursor adsorbs onto the one or more preforms;
providing a carbon-containing precursor to the reactor such that
the carbon-containing precursor reacts with the silicon-containing
precursor to form a stoichiometric precursor layer, wherein the
ratio of silicon atoms to carbon atoms in the stoichiometric
precursor layer is approximately one; and providing at least one
silicon carbide precursor to the reactor to densify the one or more
preforms by depositing a silicon carbide matrix onto the
stoichiometric precursor layer.
2. The method of claim 1, wherein the silicon carbide matrix has a
ratio of silicon atoms to carbon atoms, and the ratio is
approximately one.
3. The method of claim 1, wherein the silicon-containing precursor
includes one of Cl.sub.2SiH.sub.2, SiH.sub.4, ClSiH.sub.3, and
Si.sub.2H.sub.6 and the carbon-containing precursor includes one of
CH.sub.4 (methane), C.sub.2H.sub.6 (ethane), C.sub.3H.sub.8
(propane), C.sub.2H.sub.2 (acetylene), and C.sub.2H.sub.4
(ethylene).
4. The method of claim 1, wherein the at least one silicon carbide
precursor includes a first precursor and a second precursor, and
the first precursor is methyltrichlorosilane (MTS) and the second
precursor is hydrogen (H.sub.2).
5. The method of claim 1, further comprising the step of vacuuming
the reactor after the step of providing the silicon-containing
precursor to the reactor to remove excess silicon-containing
precursor from the reactor.
6. The method of claim 1, further comprising the step of vacuuming
the reactor after the step of providing the carbon-containing
precursor to the reactor to remove excess carbon-containing
precursor from the reactor.
7. The method of claim 1, wherein the reactor includes an exhaust
valve, and wherein the exhaust valve is closed during the step of
providing the silicon-containing precursor to the reactor and the
step of providing the carbon-containing precursor to the reactor,
and the exhaust valve is open during the step of providing at least
one silicon-carbide precursor to the reactor.
8. The method of claim 1, wherein the one or more preforms comprise
silicon carbide fibers.
9. The method of claim 8, wherein the silicon carbide fibers are
coated with a boron nitride interfacial coating.
10. The method of claim 8, wherein the silicon carbon fibers have a
unidirectional orientation with respect to one another.
11. The method of claim 8, further comprising determining the ratio
of silicon atoms to carbon atoms in the silicon carbide matrix, and
comparing the ratio to one.
Description
BACKGROUND
This disclosure relates to a method of fabricating components, and
in particular, ceramic matrix composite (CMC) components.
CMC components typically comprise ceramic reinforcements, such as
fibers, in a ceramic matrix phase. CMC components can withstand
high temperatures and oxidative environments due to their material
properties, high strength and creep resistance, high thermal
conductivity, and relatively low weight. An example CMC component
comprises silicon carbide reinforcement embedded in a silicon
carbide matrix material.
Various techniques are used to fabricate CMC components. For
example, a preform comprising reinforcements is infiltrated with a
matrix material. The composition of the matrix material affects the
properties of the CMC component. In turn, the composition of the
matrix material can be influenced by the method of depositing the
matrix material onto the preform.
SUMMARY
A method for fabricating a component according to an example of the
present disclosure includes the steps of depositing a
stoichiometric precursor layer onto a preform, and densifying the
preform by depositing a matrix material onto the stoichiometric
precursor layer.
In a further embodiment according to any of the foregoing
embodiments, the preform comprises silicon carbide fibers.
In a further embodiment according to any of the foregoing
embodiments, the stoichiometric precursor layer is silicon carbide,
and wherein the ratio of silicon to carbon in the stoichiometric
precursor layer is approximately one.
In a further embodiment according to any of the foregoing
embodiments, the matrix material is silicon carbide and has a ratio
of silicon atoms to carbon atoms, and the ratio is approximately
one.
In a further embodiment according to any of the foregoing
embodiments, the step of depositing the stoichiometric precursor
layer onto the preform is accomplished by an atomic layer
deposition process.
In a further embodiment according to any of the foregoing
embodiments, the step of densifying the preform is accomplished by
a chemical vapor infiltration process.
In a further embodiment according to any of the foregoing
embodiments, the matrix material comprises one or more
constituents, and the method further comprises the steps of
determining the ratio of the one or more constituents to one
another, and comparing the ratio to the stoichiometric ratio of the
matrix material.
In a further embodiment according to any of the foregoing
embodiments, the depositing step and the densifying step are
performed in the same reactor.
Another method of fabricating a component according to an example
of the present disclosure includes the steps of arranging one or
more preforms in a reactor, providing a silicon-containing
precursor to the reactor such that the silicon-containing precursor
adsorbs onto the one or more preforms, providing a
carbon-containing precursor to the reactor such that the
carbon-containing precursor reacts with the silicon-containing
precursor to form a stoichiometric precursor layer, wherein the
ratio of silicon atoms to carbon atoms in the stoichiometric
precursor layer is approximately one, and providing at least one
silicon carbide precursor to the reactor to densify the one or more
preforms by depositing a silicon carbide matrix onto the
stoichiometric precursor layer.
In a further embodiment according to any of the foregoing
embodiments, the silicon carbide matrix has a ratio of silicon
atoms to carbon atoms, and the ratio is approximately one.
In a further embodiment according to any of the foregoing
embodiments, the silicon-containing precursor includes one of
Cl.sub.2SiH.sub.2, SiH.sub.4, ClSiH.sub.3, and Si.sub.2H.sub.6 and
the carbon-containing precursor includes one of CH.sub.4 (methane),
C.sub.2H.sub.6 (ethane), C.sub.3H.sub.8 (propane), C.sub.2H.sub.2
(acetylene), and C.sub.2H.sub.4 (ethylene).
In a further embodiment according to any of the foregoing
embodiments, the at least one silicon carbide precursor includes a
first precursor and a second precursor, and the first precursor is
methyltrichlorosilane (MTS) and the second precursor is hydrogen
(H.sub.2).
In a further embodiment according to any of the foregoing
embodiments, the method further comprises the step of vacuuming the
reactor after the step of providing the silicon-containing
precursor to the reactor to remove excess silicon-containing
precursor from the reactor.
In a further embodiment according to any of the foregoing
embodiments, the method further comprises the step of vacuuming the
reactor after the step of providing the carbon-containing precursor
to the reactor to remove excess carbon-containing precursor from
the reactor.
In a further embodiment according to any of the foregoing
embodiments, wherein the reactor includes an exhaust valve, and
wherein the exhaust valve is closed during the step of providing
the silicon-containing precursor to the reactor and the step of
providing the carbon-containing precursor to the reactor, and the
exhaust valve is open during the step of providing at least one
silicon-carbide precursor to the reactor.
In a further embodiment according to any of the foregoing
embodiments, the one or more preforms comprise silicon carbide
fibers.
In a further embodiment according to any of the foregoing
embodiments, the silicon carbide fibers are coated with a boron
nitride interfacial coating.
In a further embodiment according to any of the foregoing
embodiments, the silicon carbon fibers have a unidirectional
orientation with respect to one another.
In a further embodiment according to any of the foregoing
embodiments, further including the step of determining the ratio of
silicon atoms to carbon atoms in the silicon carbide matrix, and
comparing the ratio to one.
A ceramic matrix composite component according to an example of the
present disclosure is formed by a process comprising the steps of
depositing a stoichiometric precursor layer onto a preform and
densifying the preform by depositing a matrix material onto the
stoichiometric precursor layer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A schematically shows a ceramic matrix composite (CMC)
component.
FIG. 1B schematically shows a close-up view of the CMC
component.
FIG. 2 schematically shows a method of fabricating the CMC
component.
FIG. 3 schematically shows a furnace for fabricating the CMC
component.
FIG. 4 schematically shows a CMC component during fabrication.
FIG. 5 schematically shows a method depositing a stoichiometric
precursor layer onto a preform.
FIG. 6 schematically shows a method of densifying a preform with a
stoichiometric precursor layer to form a CMC component.
FIG. 7 schematically shows a CMC component during the densifying
step.
DETAILED DESCRIPTION
FIGS. 1A-1B schematically illustrate a ceramic matrix composite
(CMC) component 20 for hot sections of gas turbine engines, which
operate at temperatures greater than 2000.degree. F.
(1093.33.degree. C.). In the example of FIG. 1, the component 20 is
a blade or vane for a turbine. However, in other examples,
component 20 can be another part of a gas turbine engine, such as a
combustor panel, a blade outer air seal, or another type of
component.
CMC component 20 includes ceramic reinforcements 22, such as
fibers, embedded in a ceramic matrix material 24. In the example of
FIG. 1, the fibers 22 are arranged unidirectional with respect to
one another. However, in other examples, the fibers 22 can have
other orientations, or have random orientations. In a particular
example, fibers 22 are silicon carbide fibers and matrix 24 is
silicon carbide as well. In some examples, fibers 22 include a
coating, such as a boron nitride interfacial coating.
FIG. 2 shows a method 100 of fabricating the CMC component 20. In
step 102, one or more preforms 26 are arranged in a reactor 28, as
shown in FIG. 3. The reactor 28 generally includes an inlet valve
29 to control inlets to the reactor 28 and an exhaust valve 30 to
control exhaust from the reactor 28. A vacuum pump 31 controls the
pressure in the reactor 28.
The preforms 26 comprise fibers 22 and are generally porous. In the
example of FIG. 3, multiple preforms 26 are loaded to the reactor
28 and are stacked, with spacers 27 separating each preform 26 from
adjacent preforms 26. In another example, preforms 26 can be
arranged within reactor 28 in another way. In yet another example,
only a single preform 26 is loaded to the reactor 28. For ease of
reference, a single preform 26 will be referred to in the foregoing
description.
In step 104, a stoichiometric precursor layer 32 is infiltrated
into the preform 26, as shown in FIG. 4. A stoichiometric material
such as the stoichiometric precursor material has a ratio of atomic
constituents that is approximately the same as the ratio of
constituents expressed in its chemical formula. For instance,
stoichiometric silicon carbide (SiC) has a ratio of silicon atoms
to carbon atoms that is equal to approximately one. Silicon carbide
with a ratio of silicon atoms to carbon atoms that is substantially
equal to one (i.e., "stoichiometric silicon carbide") exhibits
improved temperature and oxidation resistance, as well as high
thermal conductivity and high strength and creep resistance as
compared to silicon carbide with a ratio of silicon atoms to carbon
atoms that is substantially less than or greater than one. This is
partially due to improved material uniformity. Additionally, if
silicon carbide has a ratio of silicon atoms to carbon atoms
greater than one, the silicon carbide has excess silicon and
exhibits lowered melting temperature and lowered oxidation
resistance. Likewise, if silicon carbide has a ratio of silicon
atoms to carbon atoms less than one, the silicon carbide has excess
carbon and exhibits decreased temperature and oxidation resistance.
Though in this example, the stoichiometric precursor layer 32 is
silicon carbide, it should be understood that in other examples,
the stoichiometric precursor layer 32 is another stoichiometric
material.
In one example, the stoichiometric precursor layer 32 is deposited
into the one or more preforms 26 by an atomic layer deposition
(ALD) process. In a particular example an atomic layer epitaxy
(ALE) process is used. An ALE process 200 is shown in FIG. 5. In
step 202, a gas 34 that is inert is provided to the reactor 28 by
opening valve 36.
In step 204, the reactor 28 is then brought to a desired
temperature T1 and a desired pressure P1. The desired temperature
T1 and pressure P1 depend on selected and used precursors and the
desired stoichiometric precursor layer 32. In one example, where
the desired stoichiometric precursor layer 32 is silicon carbide,
the desired temperature T1 is about 1832.degree. F. (1000.degree.
C.) and the desired pressure P1 is about 0.3 torr (40 Pa).
In step 206, a first precursor 38 is provided to the reactor 28 by
opening valve 40. At the same time, valve 36 is closed to stop the
flow of gas 34 into the reactor 28 and exhaust valve 30 is closed
to keep the first precursor 38 in the reactor 28. In one example,
step 206 is performed in approximately ten seconds or less. The
first precursor infiltrates into and adsorbs on the surfaces of the
preform 26. For the silicon carbide stoichiometric precursor layer
32 discussed above, the first precursor is a silicon-containing
precursor and the second precursor is a carbon-containing
precursor. Example silicon-containing precursors are
Cl.sub.2SiH.sub.2, SiH.sub.4, ClSiH.sub.3, and Si.sub.2H.sub.6.
Example carbon-containing precursors are CH.sub.4 (methane),
C.sub.2H.sub.6 (ethane), C.sub.3H.sub.8 (propane), C.sub.2H.sub.2
(acetylene), and C.sub.2H.sub.4 (ethylene). However, if another
stoichiometric precursor layer 32 is being formed, other precursors
containing the elements of the desired stoichiometric precursor
layer 32 would be used. At the end of step 206, valve 40 is closed
to stop the flow of the first precursor 38 into the reactor 28.
In step 208, the reactor 28 is vacuumed by vacuum pump 31 by
opening exhaust valve 30 to remove excess first precursor 38 from
the reactor 28. In one example, step 208 is performed for
approximately between ten and 60 seconds.
In step 210, a second precursor 42 is provided to the reactor 28 by
opening valve 44. At the same time, exhaust valve 30 is closed to
keep the second precursor 42 in the reactor 28. During step 210,
the precursors 38, 42 form the stoichiometric precursor layer 32
(i.e., a layer 32 with a ratio of silicon atoms to carbon atoms of
approximately one). In the example of a silicon carbide
stoichiometric precursor layer 32, the second precursor 42 is a
carbon-containing precursor and infiltrates the preform 26 to form
the silicon carbide, such that the ratio of silicon atoms to carbon
atoms on the preform 26 is approximately one. In one example, step
210 is performed in approximately ten seconds or less. At the end
of step 210, valve 44 is closed to stop the flow of the second
precursor 42 into the reactor 28. For example, silicon and carbon
from the precursors 38, 42 form a silicon carbide stoichiometric
precursor layer, as shown in FIG. 4. In one example, the first
precursor 38 is the silicon-containing precursor and the second
precursor 42 is the carbon-containing precursor.
In step 212, the reactor 28 is vacuumed by pump 31 by opening
exhaust valve 30 to remove the second precursor 42 from the reactor
28. In one example, step 212 is performed for approximately between
ten and 60 seconds.
Steps 206-212 can optionally be repeated one or more times to build
up the stoichiometric precursor layer 32.
Referring again to FIG. 2, in step 106, the component 20 is
densified by depositing matrix material 24 onto the stoichiometric
precursor layer 32. The matrix material 24 is the same material as
the stoichiometric precursor layer 32. The stoichiometric precursor
layer 32 favors improved yield and deposition of a generally
stoichiometric matrix material 24 in step 106. This is because
reactions occurring at the surface of the preform 26 tend to mimic
the existing surface chemistry of the stoichiometric precursor
layer 32 to mitigate the stacking faults. Therefore, the matrix
material 24 is generally stoichiometric and exhibits improved
properties as described above.
In one example, steps 104-106 are repeated one or more times. For
instance, after partially densifying the preform 26 in step 106,
the ratio of the constituents of the matrix material 24 is
determined via x-ray or another type of spectroscopy in optional
step 108. Then, the ratio of constituents is compared to the
stoichiometric ratio in step 110. If the ratio differs from the
stoichiometric ratio, another stoichiometric precursor layer 32 is
infiltrated into the preform 26 as in step 104. The preform 26 is
then densified again as in step 106. The further densification
results in a generally stoichiometric matrix material 24 as
described above.
In one example, the densifying in step 106 is performed by a
chemical vapor infiltration process 300, as shown schematically in
FIG. 6.
In step 302, the reactor 28 is brought to a desired temperature T2
and pressure P2. For example, for the deposition of silicon carbide
matrix material 24 with precursors methyltrichlorosilane (MTS) and
hydrogen (H.sub.2), as will be discussed below, the reactor is
brought to a temperature T2 of approximately 1922.degree. F.
(1050.degree. C.) and a pressure P2 10 torr (1333.22 Pa). In
another example, the temperature T2 in process 300 is greater than
the temperature T1 in process 200, and the pressure P2 in process
300 is greater than the pressure P1 in process 200.
In step 304, one or more matrix material precursors 46a, 46b are
provided to the reactor 28. Exhaust valve 30 remains open to allow
for continuous flow of matrix material precursors 46a, 48b through
the reactor 28, as shown by arrows F. For a silicon carbide matrix
material 24, example precursors 46a, 46b are methyltrichlorosilane
(MTS) and hydrogen (H.sub.2). In this example, during step 304, MTS
breaks down into gaseous CH.sub.3 and SiCl.sub.3 free radicals 50,
as shown in FIG. 7, which adsorb onto the stoichiometric precursor
layer 32 to react for the formation of silicon carbide deposit, in
generally stoichiometric amounts to create a generally
stoichiometric silicon carbide matrix material 24. Step 304 is
performed until a desired density of the component 20 is
achieved.
In one example, MTS is provided to the reactor 28 by opening valve
48 and hydrogen is provided to the reactor 28 by valve 36, the same
valve that controls flow of inert gas 34 to the reactor 28. In
another example, a separate valve is used for hydrogen or another
matrix material precursor.
In step 306, the reactor 28 is purged by closing valve 48 to stop
the flow of matrix material precursor 46a into the reactor 28 and
providing inert gas 34 to the reactor 28 via valve 36. In step 306,
the reactor 28 is also cooled.
Though steps 104 and 106 are described above as being performed in
the same furnace, in another example, steps 104 and 106 can be
performed in separate furnaces.
Furthermore, the foregoing description shall be interpreted as
illustrative and not in any limiting sense. A worker of ordinary
skill in the art would understand that certain modifications could
come within the scope of this disclosure. For these reasons, the
following claims should be studied to determine the true scope and
content of this disclosure.
* * * * *